In December 2021, four sediment push cores (core names appended with 'M' for marsh push core) and peat augers (core names appended with 'R' for Russian peat auger) were collected from the marshes of Deer Island, Mississippi during U.S. Geological Survey (USGS) field activity number (FAN) 2021-351-FA. Select intervals from the manual push cores were analyzed for determination of lead-210 activities via alpha spectroscopy for development of accumulation rates using standard model methods. Twenty percent of push core samples were counted in triplicate for determination of a lead-210 activity standard deviation. Select intervals were also run on gamma spectroscopy for lead-210 activity validation and cesium-137 activities. Peat augers were collected for determination of peat thickness and were discarded in the field once described and photographed. Core locations were recorded concurrently using real-time kinematic (RTK) positioning for collection of latitude, longitude and elevation (North American Datum of 1983 (2011) [NAD83_2011] and North American Vertical Datum of 1988 [NAVD88], GEOID12B respectively).